kernel panic-not syncing:VFS:Unable to mount root fs on unknown-block

According to the feedback from the merchant, a user's host could not be accessed. After checking with VNC, the system failed to boot normally. The prompt message was: kernel panic-not syncing: VFS: Unable to mount root fs on unknown-block. The host was a CentOS system. This situation usually occurs after upgrading the kernel.

Solution: Reboot and select the old version kernel to boot into the system .

Since the merchant uses Yungu's Xensystem+nokvm system, the management page has integrated the vnc console. We can first restart the host on the VPS management page, then log in to the VNC console, and press the up and down arrow keys when booting to the system list, select the appropriate kernel and press Enter.

Please note that it is very fast to boot to the page shown above. If you are a little slower when logging into VNC, you may not see this page at all. It is recommended to open two VPS management windows, one for clicking restart and one for VNC console.

After successfully entering the system, we can modify the kernel default boot sequence. CentOS7 uses grub2 as the boot program.